Vehicles having automatic transmissions change gear ratios based on vehicle speed and driver acceleration demand. During deceleration automatic transmissions shift through progressively lower gear ratios. The smoothness of the shifting from a given gear to the next adjacent gear influences noise, vibration, and harshness as perceived by the driver.
Hybrid vehicles may employ one or more electric machines having a motor-generator in combination with an internal combustion engine. Depending on vehicle operating conditions, the electric machine may selectively alternate between serving as a motive power source, or a decelerating load upon the powertrain.